My goal is to instal Team Fortress 2 onto the Ubuntu part so I can play TF2 in Linux.

So far everything has gone well from installing steam to transfering the TF2 backup over so I would not have to redownload the 12GB. However, this is where the trouble arises. I cannot remember the specific amount of space that I allowed ubuntu when I installed it, but it is not enough.

How can I increase the space that Ubuntu can use so that I can instal Team Fortress 2?